Preparation of lead alkyls



Patented May 7, 1935' Emi -em V .-=2,000,069' V ntertainers 0F LEADALKYLs rreaericwnrimwn' mg, cameyyrism, aim Louis si -Bakepfennsgtove,

' e 1 an 51 New & fl nivan fi' n f Del.,'a corporationnf Delaware (i-Drawing; Ai'iiilicatipn 'EMay 3 24,. 1932, Sei-ialZ-No. 813,260

i fllhislliiivention deletes to am i'fiiproifme'nt' in .zthejproduction-of lead' alkyls by he mman nt alk-yl halides upon a=leadsodiuni aHoyfand -iriore particularly to the alloys' en-iployedirisucl1' p'roc :ilrr theprocessiasord' 'arily 'practi'ced at t-he.spresent timeiiaiilead sodium alloy consistin 'of lead and I0 sodium isreacted vvith 'ethyl fichloridektoefor-m a' dry reaction -meisscontaining lead alkyl absorbed by finely dividd lead, rsodiumihalide andan 'iappreciable amoiint of *un'd'ecomposedi alloy. Theilead alkylis'recovered from; the .mass: 'bys drowning in wat'er and 'liistillingroutthelead 'alliyl by meansof stam B'y the usezofsuch-.proc'ess,'=*ezriploying ethyl-chloride, yields of fromz'83a%' OF35'%-of itetra- 'e'thyl lald have beenf'obtaind the laboratory, with amountsof about -5%ltoi il0 of the alloy left undecomposed. Such undecomposedsodium tends to cause trouble in the recovery of the alkyl leadcompounds by steam distillation, due to the fact that the undercomposedsodium. reacts with the water in which the reaction mass is drowned withthe result that the metalic lead tends to form large balls, cakes orrings which lower the recovery of the alkyl lead and are removed fromthe still only with great difficulty.

In order to eliminate this balling of the lead, as

much as possible, it has been necessary to add a. protective agent suchas, for example, thiocarbam'lide or a dispersing agent such as engineoil, or both, to the reaction mass during distillation. However, theseexpedients have not proved to be entirely satisfactory as a largepercentage of the distillations give trouble even in the presence ofthese substances.

An object of the present invention is to provide a process wherein thesedifliculties are eliminated. A further object is to provide a newcomposition of matter in the nature of an alloy to be used in suchprocess which composition of matter is substantially completelydecomposed during the reaction and has no tendency to cause balling orcaking of the metallic lead. Still further objects are to provide a newcomposition of matter and to advance the art. Other and further objectswill appear hereinafter.

These objects may be accomplished according to our invention whichcomprises substituting for a small proportion of the lead, in the leadsodium alloy of the process as heretofore practiced, a small amount ofmagnesium. We have found that when'amounts of magnesium varying from0.05% to 1.0% of the weight of the alloy is substituted for anequivalent weight of'"thelead'in'the preparation'ofthe'alloy andsucmnevw compositicm bf matter. is use'dfimi the inanufactureof l'ead'--'alkyl compounds, higher yields am ne 1m :aikyi compounds.- 'resultitlie comp'osi-tibmis mor completely:*deeom osdiduringdbhs actionraxidagglomeration of the Head particles during distillation ispractica'l'ly' elimi n'ated without re'qui'ring the use of a =protectiweor dispersing agent. f'li on eka-mple," when uch --compositiorfiofirnatter is employed in -'the proj duction of t etra ethylrl eadgi'yieldsofiwfnonii about 185%flto 88 701 215obtained and .thel amount'liof iundecompcsed composition the 'reaction;-mass at the eempiemcm of therea'ctio'n amounts to fro'm 4 to 0%g both 'theyield ofrtetra ethylfile'ad ndfitlieiamount of undecompo'sed composiitiomdeperiding upon theammmt bf magnesium present in the*izomposition employed. :flt :has beenfound that as little as 0.1% of magnesium in the composition issufficient to practically eliminate all agglomeration of lead particlesduring the distillation, which appears to be due to the fact'that a muchmore complete reaction is obtained with less undecomposed compositionpresent in the reaction mass. However, we preferably employ from about0.15% to 0.4% of magnesium as such amount gives most satisfactoryresults. In order to more clearly point out our invention and illustratethe preferred mode in which we contemplate carrying the same intoeffect, the following examples are given:

Example 1.One hundred grams of a lead-sodium alloy containing 90% leadand 10% sodium by weight, equivalent to equalmolecular 1'.

proportions of the two metals, were reacted with 50 cc. of ethylchloride in a small pressure autoclave in. a water bath of 75 C. for 5hours. The resultant reaction mass was drowned in. 500 cc. of water andthe lead ethyl distilled off, with. steam. The weight of lead ethylrecovered was 29.2 grams, equivalent to 84.3% yield, based on thesodium.

The unreacted sodium which was present as sodium hydroxide in theresidue from the steam distillation was determined by titration withstandard acid solution and the results calculated as sodium. Thisunreacted sodium was found to be 0.51 grams or 5.1%.

Example 2.-One hundred (100) grams of magnesium bearing lead sodiumalloy consisting of 89.6% lead, 10% sodium and 0.4% magnesium werereacted with 50 cc. of ethyl chloride and the lead ethyl recovered inthe same manner as recited in Example 1.. The yield of the lead ethyl Iwas found to be 30.98 grams or 88.1% based on the sodium.

No unreacted sodium was present in the reaction mass as shown by thefact that the residue from the steam distillation torremove the leadtetra, ethyl, was neutral to phenol phthalein.

The results obtainable by varying the amounts of lead and magnesium in"the composition are shown in the following table:

Alloy Yield based on sodium per- Undecom- V centage of posed alloy LeadNa Mg theory Percent Percent Percent Percent 90 l 0 84. 3 52 1 89. 9 100. 1 86. 2 4 2 89. 8 10 0. 2 87. 3 2. 5 89. 7 0.3 88.0 w 1. 0 89. 6 100. 4 88. 1 0.0 89. 5 10 0. 5 87. 0 0 0 89. 0 10 1. 0 86. 0 0 0 Althoughthe use of about 0.4% of magnesium in the composition appears to be mostdesirable from a theoretical standpoint, we have found that, forpractical purposes, the use of from about ,0.15% to 0.2% ofmagnesiumispreferable as larger amounts introduce certain problems intothe manufacture ofpthe composition and the recovery of the alkyllead'compounds.

invention is to be limited solely by the appended claims construed asbroadly as is permissible in view of the prior art.

We claim:

1. The method of producing lead alkyls which comprises reacting an alkylhalide with a composition of matter comprising 10% sodium, 89.95% to89.00% lead and 0.05% to 1.00% magnesium.

a 2. The method of producing lead alkyls which comprises reacting analkyl halide with a composition of matter comprising 10% sodium, fromabout 89.85% to 89.80% lead and from about 0.15% to 0.20% magnesium.

3. The method of producing lead alkyls which comprises reacting an alkylchloride with a composition of matter comprising 10% sodium, 489.95% to89.00% lead and 0.05% to 1.00%

magnesium.

4. The method of producing lead alkyls which comprises reacting an alkylchloride with a composition of matter comprising 10% sodium, fromabout.89.85% to 89.80% lead and from about 0.15% to 0.2 0% magnesium.

5. The method of producing tetra ethyl lead which comprises reactingethyl chloride with a composition of matter comprising 10% sodium,89.95%to 89.00% lead and 0.05% to 1.00% magnesium and distilling off thetetra ethyl lead with steam.

6. The method of producing tetra ethyl lead which comprises reactingethyl chloride with a compositionofmatter comprising 10% sodium, fromabout 89.85% to 89.80% lead and from about 0.15%, to 0.20% magnesium anddistilling on the tetra ethyl lead with steam.

FREDERICK B. DOWNING.

LOUIS S BAKE.

